1. Field of the Invention
The present invention relates generally to an image processing method and apparatus, and more particularly, to an image processing apparatus such as a digital camera, which captures a still frame and performs image processing with respect to the captured frame, and an image processing method for correcting hand-shake by using a composite synthesizing technique.
2. Description of the Related Art
Composite synthesis, which is also referred to as still frame Electronic Image Stabilization (EIS), is a noise cancellation technique based on superposition of a plurality of images, and is used for hand-shake correction in a camera of a device such as a cellular phone. In hand-shake correction, a plurality of images are automatically and continuously captured within a short time through one-time capturing manipulation by a manipulator, and each image is superposed with correction of an error (discrepancy) caused by hand-shake. For this reason, a technique such as pixel shift or shape correction is required.
FIG. 1 illustrates a conventional technique for hand-shake correction.
In FIG. 1, a continuously captured image output from a sensor is developed and stored in an internal memory such as a Synchronous Dynamic Random Access Memory (SDRAM). Feature points of a plurality of images are detected. By comparing these feature points, motion detection is performed, it is determined whether an image is moved due to hand-shake or distorted through inclination, and pixel shift or affine conversion is performed. This result is additive-synthesized, thus performing composite synthesis.
However, there are various techniques for composite synthesis, such as motion vector detection and image object recognition.
For a range of motion detection, there exists only a technique for properly setting a limit of hand-shake by a manipulator and determining a maximum necessary range from the limit. For example, Japanese Patent Publication No. 2006-86741 discloses requiring the maximum shake amount on an image from a focal length, a pixel pitch, and the maximum width of hand-shake, and searching the range.
However, because of the manipulator, it is difficult to predict the limit of hand-shake in view of such variables as a composition of the camera, and a manner by which to hold the camera and the manipulator. If a range of motion detection is properly set with a margin as in a conventional technique, a heavy load is imposed on image processing in superposition. For this reason, it is required to set the range as narrow as possible. To this point, however, the prior art has not considered this requirement.